Japanese Patent Application Publication Kokai 2003-72329 proposes a production process for a pneumatic tire with a puncture preventing function by which a rubber layer containing a peroxide and a rubber layer not containing a peroxide are applied on the internal surface of an unvulcanized tire prior to vulcanization molding. The tire is then vulcanized so that the first rubber layer is decomposed by the peroxide to form a sealant layer while the second rubber layer forms a cover sheet layer that covers the sealant layer.
However, with this production method, when the rubber component that forms the sealant layer is decomposed by the peroxide, a large quantity of decomposition gas is generated. Because this decomposition gas is retained between the sealant layer and the cover sheet layer, the sealant layer becomes nonuniform. Consequently, a process of removing the gas after vulcanization molding is required, leading to problems with inferior productivity.
Forming a sealant layer and a cover sheet layer on the pneumatic tire after vulcanization molding is useful in order to eliminate the need for this gas removal process. However, the viscosity of the sealant material is high, so an organic solvent must be added to the sealant material to decrease the viscosity and make handling easier in order to apply it as a uniform sheet onto the internal surface of the tire. As a result, an inconvenient process of removing the solvent is required after applying the sealant material to the internal surface of the tire, and if there is residual organic solvent, there will be safety problems associated with evaporation when the tire is in use. Furthermore, if the sealant material is applied without using an organic solvent, a high-pressure apparatus is required in order to apply the high viscosity sealant material in a strip, or a high precision control apparatus is required to perform a complicated operation using a nozzle that sprays sealant in order to form a uniform sheet on the internal surface of the tire, and therefore there is a problem of increased production costs.